Hi Chenggang,
Have a doubt about the old code.
On 2018/4/12 PM 12:58, chenggang.qin@linux.alibaba.com Wrote:
From: Andy Lutomirski luto@kernel.org
commit: 9d05041679904b12c12421cbcf9cb5f4860a8d7b upstream
32-bit kernels handle nested NMIs in C. Enable the exact same handling on 64-bit kernels as well. This isn't currently necessary, but it will become necessary once the asm code starts allowing limited nesting.
...... -static inline void nmi_nesting_preprocess(struct pt_regs *regs) +dotraplinkage notrace void +do_nmi(struct pt_regs *regs, long error_code) {
- if (this_cpu_read(nmi_state) != NMI_NOT_RUNNING) {
this_cpu_write(nmi_state, NMI_LATCHED);return;- }
- this_cpu_write(nmi_state, NMI_EXECUTING);
- this_cpu_write(nmi_cr2, read_cr2());
+nmi_restart:
Here if there are more than 2 NMIs nested, but the nmi_state is always NMI_LATCHED.
- /* On i386, may loop back to preprocess */
- nmi_nesting_postprocess();
- if (unlikely(this_cpu_read(nmi_cr2) != read_cr2()))
write_cr2(this_cpu_read(nmi_cr2));- if (this_cpu_dec_return(nmi_state))
goto nmi_restart;
But here at most re-execute 2 NMIs, so some nmi lost ? And cr2 is always the first NMI's cr2. CR2 is wrong for the later NMIs.
void stop_nmi(void)
Thanks & Regards Qixuan Wu.